Functionalized Silica Nanoparticles for Enhanced Heavy Oil Recovery: Experiment and Molecular Dynamics Simulation

Conventional chemical enhanced oil recovery (EOR) methods encounter significant challenges in heavy oil reservoirs, such as surfactant adsorption, thermal degradation, and unstable emulsions under harsh conditions. These limitations underscore the need for alternative EOR agents with enhanced performance characteristics. In this study, cost-effective silica nanoparticles were employed as a substrate material and functionalized through surface grafting of sodium alpha-olefin sulfonate and Poloxamer (F127) to synthesize the modified nanomaterial SAP. The performance and mechanisms of SAP in EOR were comprehensively investigated. The structure of SAP was characterized using 1 H NMR, FTIR, and TGA, while its interfacial activity, stability, emulsification capacity, and oil displacement performance were comprehensively assessed. Additionally, molecular dynamics simulations were performed to explore the microscopic mechanism of viscosity reduction. The results revealed that a 100 ppm of SAP solution reduced the oil–water interfacial tension from 21.6 to 1.25 mN/m. After 72 h of immersion in SAP solutions, the contact angle of oil-wet rock surfaces decreased from 134° to 33.5°, converting the surface from oil-wet to water-wet. The absolute zeta potential consistently exceeded 30 mV within 168h, confirming colloidal stability of the SAP solution. SAP effectively forms low-viscosity oil-in-water (O/W) emulsions with oil, reducing viscosity by 95% at 80% aqueous phase content. Core flooding experiments reveal that the SAP system EOR by 27.3% when combined with subsequent water flooding. Molecular simulations further indicate that SAP interacts with asphaltenes in oil, organizing and localizing their arrangement to form stable O/W emulsion structures. This interaction minimizes direct contact and aggregation of oil droplets, promoting their uniform dispersion in water and significantly reducing overall viscosity. This study offers valuable insights into nanomaterial application for enhancing heavy oil recovery and highlights the potential of SAP as a novel viscosity reducer and emulsifier.